"The episode was written by Steven Moffat, who co-created the series. It was originally filmed as a 60-minute pilot for Sherlock, directed by Coky Giedroyc. However, the BBC decided not to transmit the pilot, but instead commissioned a series of three 90-minute episodes. The story was refilmed, this time directed by Paul McGuigan. The British Board of Film Classification has rated the pilot as a 12 certificate (not suitable for children under 12) for video and online exhibition, and it is included as an additional feature on the DVD released on 30 August 2010."